# Acute Alcohol‐Induced Changes Measured With Metabotropic Glutamate Receptor 5 Positron Emission Tomography

## TL;DR

This study shows that a PET imaging technique can detect brain changes caused by acute alcohol consumption in humans, supporting its use for future alcohol-related research.

## Contribution

The study demonstrates the first human application of [11C]ABP688 PET to detect acute alcohol-induced glutamatergic changes.

## Key findings

- Acute alcohol significantly decreased [11C]ABP688 BPND across brain regions.
- Alcohol increased [11C]ABP688 R1, indicating increased relative blood flow.
- Higher blood alcohol levels correlated with greater changes in R1 in cortical regions.

## Abstract

Alcohol consumption at clinically relevant doses alters brain glutamate release. However, few techniques exist to measure these changes in humans. The metabotropic glutamate receptor 5 (mGluR5) PET radioligand [11C]ABP688 is sensitive to acute alcohol in rodents, possibly mediated by alcohol effects on glutamate release. This study aimed to determine the sensitivity of [11C]ABP688 PET to an acute alcohol challenge in humans.

Eight social drinkers (25–42 years; 5 females) with a recent drinking occasion achieving a blood alcohol level (BAL) > 80 mg/dL were recruited. All participants underwent a 90‐min dynamic baseline [11C]ABP688 PET scan. Two weeks later (range: 7–29 days), participants completed an oral laboratory alcohol challenge over 30 min, targeting a BAL of 60 mg/dL. Immediately after the challenge, a second [11C]ABP688 PET scan was performed. Non‐displaceable binding potential (BP
ND; indicative of mGluR5 availability) and R
1 (indicative of relative blood flow) were estimated using the simplified reference tissue model with the cerebellum as the reference region. Blood samples were taken throughout the scanning procedure to measure the BAL.

Seven participants (4 females) completed the study. The mean peak BAL achieved was 61 ± 18 mg/dL. Acute alcohol significantly decreased [11C]ABP688 BP
ND, F(1, 42) = 17.05, p < 0.001, Cohen's d = 0.32–0.60, and increased [11C]ABP688 R
1, F(1, 42) = 6.67, p = 0.013, Cohen's d = 0.32–0.48, across brain regions. Exploratory analysis showed a positive relationship between alcohol‐induced % change in [11C]ABP688 R
1 in cortical regions and peak BAL (Spearman rho = 0.78 [frontal cortex] and 0.85 [temporal cortex] = 0.024 and 0.011).

This proof‐of‐concept study demonstrates that [11C]ABP688 PET imaging is sensitive to the effects of acute alcohol consumption. The observed decrease in mGluR5 availability aligns with preclinical data potentially indicating acute increased extracellular glutamate concentrations following ethanol dosing. This imaging tool could be useful for future investigations into the acute effects of alcohol on the brain during abstinence and withdrawal.

This proof‐of‐concept study provides evidence that acute alcohol administration reduces mGluR5 availability and increases relative blood flow in the human brain, as measured by [11C]ABP688 PET. The observed effects align with preclinical evidence of alcohol‐induced glutamate release. These findings support the utility of [11C]ABP688 PET for probing glutamatergic changes during alcohol exposure in humans.